1. Field of the Invention
The invention relates to the field of electronic thermostats and more particularly to a programmable electronic thermostat.
2. Description of Related Art
There are several programmable thermostats now available in the market. To operate these thermostats, a user may select a plurality of times within a day and assign a desired temperature to each time. Alternatively, a plurality of times and temperatures may be pre-programmable by the manufacturer and stored in a long-term or permanent memory such as a Read Only Memory (ROM). This information is then transferred and stored in a working memory such as a Random Access Memory (RAM). The thermostat then controls a heating and/or cooling system according to the programmed times and temperatures, i.e., a program set, in a well known manner. As used herein, the term "program set" shall refer to a group of programs, each program including a starting time and corresponding temperature. For example, the times and temperatures associated with program numbers 1-4 in Table 1 constitute a program set. An example of one program set having four programs for a heating cycle or mode is shown in Table 1.
TABLE 1 ______________________________________ Prog. Time Temperature Remarks ______________________________________ 1 6:00 A.M. 68.degree. C. Wakeup 2 8:00 A.M. 60.degree. C. No one at home 3 3:30 P.M. 69.degree. C. Children return home 4 11:00 P.M. 63.degree. C. Sleep ______________________________________
As shown in Table 1, four start times and temperatures within a day are entered to define the program set. These entries are designated by program numbers (1-4). A time and a temperature is associated with each of these program numbers. The remarks are provided as an explanatory device for this example. In this example, at 6:00 A.M., the temperature is set at 68.degree. F. This corresponds to a time when the user would normally wake up. By 8:00 A.M., the user leaves the house, and the temperature may be lowered. Thus, at 8:00 A.M., the temperature setting is lowered to 60.degree. F. At 3:30 P.M. the user's children return to home, and it is desirable to raise the temperature to 69.degree. F. Finally, at 11:00 P.M., the user goes to sleep, and the temperature is again lowered, i.e., to 63.degree. F. Table 1 represents a single example of a program set containing a plurality of program times and temperatures which may be used to vary the temperature throughout the day based on the user's (or the user's family's) schedule, which the thermostat is to control. It is to be understood that other program sets may be desirable for other users.
A program set may be provided or transferred to a working memory or Random Access Memory (RAM) of the programmable thermostat in many different ways. As discussed above, the program set may be programmed by the user in accordance with instructions provided to the user either in a separate instruction manual or by prompts displayed on the thermostat display. Alternatively, the thermostat may include a pre-programmed program set created by the thermostat manufacturer that resides in a permanent or long term memory, such as the ROM, which pre-programmed program set is either automatically transferred into the working memory upon system initialization, from which the user can then alter according to his or her needs, or the manufacturer may have a plurality of program sets stored in the long term memory which a user can select to be transferred into the working memory. Further, programmable thermostats are known where such plural program sets, any one of which may be transferred into the working memory, may be altered by the user to create a special program set. An example of a programmable thermostat is described in U.S. patent application Ser. No. 08/665,206 filed on Jun. 14, 1996, entitled AUTO-PROGRAMMABLE ELECTRONIC THERMOSTAT, inventor V. Mehta, and assigned to the same assignee as the present application. See also, U.S. Pat. No. 5,329,991, assigned to the same assignee as another example of a programmable thermostat.
The programmable thermostats of the type described above are advantageous in that they permit the thermostat to control the heating and/or cooling operation within an environment that changes over the day in accordance with the user's particular schedule, thus saving energy costs. However, circumstances exist where the user's schedule is altered and requires the user to remain at home on a particular day, which then requires the user to either suffer through periods of undesirable temperature settings or having to re-program the thermostat in a manner that the user may be unaccustomed to and which may be relatively complicated. Thus, a need has arisen to provide a system that accommodates the user so as to quickly and easily, and temporarily, reset the program set temperature values then stored in working memory.
Programmable thermostats are also known to include override functions whereby a user may, using the controls on the thermostat panel, override the current setpoint temperature to set back or set up a new temperature, which may remain for a fixed time period or until the start of the next program time. The override temperature setting bears no relationship to, i.e., is not a function of, the programmed temperature values.